BlackBerry :: Unable To Send MMS And Frustrated By Repetition

I have a Blackberry Torch. I used to be able to send MMS and access the internet, then my handset was replaced, and suddenly I couldn't access the internet. Now the internet is fixed but I can't send MMS. A large red cross just appears whenever I try to. When I call my provider, they say everything is active on my account, and I've had to go through the settings with them numorous times each time I call up because they don't believe me when I say I've done it all before. So basically, apparently my account and settings are all correct